There are millions of species of animal on this planet, and thousands are magical creatures. Not every magical beast is known from mythology, and not all mentioned in mythology are real. But they are out there.

Some creatures in folklore are real, but when to determine a certaun creature to be likely to exist you have to define if it's a magickal entity you haven't seen in rituals or the astral plane or just a species of animal unknown to modern science

Take sasquatch for example: judging from reports of its appearance and behavioural traits it's unlikely it's magickal. It's most likely a survivng species of prehistoric ape.

Now take a creature named the Jersey Devil for example: this is something UTTERLEY random which is a creature reported in the Pine Brarens of New Jersey. It's said to have the body of a horse, wings of a bat with a 20ft span, clawed feet and a serpent tail. This creature does seem biologically unlikely (and if you research it you find out that people find footprints in LAKES), so if it does exist it's most likely supernatural.

Creatures that seem plausible to science in legends often don't seem to act like magickal creatures from reports about them.

Well we don't know that, and therefore we have no idea if sasquatch is an unplausible magciakl entity and if the Jersey Devil is a senisble-seeming undiscovered species. We have no idea until we see one.

If there are under three reports of the creature, and if its in the exact same area, it is possibly a hallucination of trees and shadows, bushes ect.
But if there are multiple cases, each describing the creature, and each in a different section of the area at hand, I consider it true. (But thats me personally)
Some reports are just cries for attention, these often tend to involve a 'life changing attack' or 'traumatic experience'